Fourteen Turkish police were killed Tuesday in a new attack blamed on Kurdish militants as violence in the southeast threatened to spiral out of control and Ankara launched a massive wave of air strikes against rebel strongholds in northern Iraq.

The 14 police were killed in the eastern region of Igdir in a bomb attack by Kurdistan Workers' Party (PKK) militants on a minibus taking them to the Dilucu border post with neighbouring Azerbaijan, the state-run Anatolia news agency reported.

Anatolia said that 12 police were killed in Tuesday's attack, with two more losing their lives in hospital. Two others are being treated in Igdir city hospital, it said.

The attack came two days after 16 Turkish soldiers were killed in a twin roadside bomb attack in Daglica in the southeastern region of Hakkari, according to the army, the deadliest strike in the current phase of the conflict.

Their deaths prompted Prime Minister Ahmet Davutoglu to vow to "wipe out" PKK militants from the mountains of eastern Turkey.

The PKK, known for sometimes exaggerating the death tolls of its attacks, said 31 Turkish soldiers had been killed in Sunday's gun and bomb attack in Daglica.

Turkey has staged air strikes and ground operations against the PKK in its strongholds of southeastern Turkey and northern Iraq in a bid to inflict a mortal blow its capacities.

But the PKK has hit back, killing dozens of Turkish police and soldiers in almost daily attacks, with the bloodier attacks marking a new intensification of the conflict.

Turkish response

In response to the Daglica attack, Turkish warplanes launched a massive air operation early Tuesday in northern Iraq, killing as many as 40 rebels, Anatolia said.

More than 50 Turkish jets were involved in the six hours of raids, killing "35 to 40 terrorists according to preliminary findings", it added.

"These terrorists must be wiped out from the mountains," Prime Minister Ahmet Davutoglu said Monday.

"The mountains of this country, the plains, highlands, cities, will be not abandoned to terrorists," he said.

Hostages released

Meanwhile 20 customs officials who were allegedly kidnapped by the PKK in August were released on Tuesday, reported the Turkish Daily Sabah newspaper.

According to Sabah, 10 customs officers working at the Üzümlü border crossing between Turkey and Iraq were kidnapped by PKK militiamen on 10 August while they were on their way to work.

Another 10 customs officers who were reportedly kidnapped by the PKK at the Kapikoy border gate between Turkey and Iran on 21 August, were also released on Tuesday.

The officers were handed to IHD, a human rights association, and a committee from People's Democratic Party (HDP) in northern Iraq.

IHD's chairman, Ozturk Turkdogan said: "The 20 customs officers were released in a rural area near Dohuk [a governorate within Iraq's Kurdistan Region]," reported the Daily Sabah. "The IHD committee that took the delivery of the customs officers has left Dohuk for Turkey."

The violence has left in tatters a 2013 ceasefire aimed at allowing a final peace deal to end the PKK's three-decade insurgency, which has claimed tens of thousands of lives.

The PKK initially took up arms in 1984 with the aim of establishing an independent state for Turkey's Kurdish minority, although lately the demands focused on greater autonomy and rights.

Commentators have expressed alarm that the current situation increasingly resembles the worst days of the PKKs insurgency in the 1990s when attacks on this scale were commonplace.

In a scene that has become familiar over the last weeks, Davutoglu will later Tuesday attend a funeral ceremony for the soldiers killed in the Daglica attack in the eastern city of Van.

The unrest comes at an explosive time in Turkey as the country prepares to hold snap elections on 1 November following June polls where President Recep Tayyip Erdogan's ruling party lost its overall majority as a pro-Kurdish party made a major breakthrough.

Davutoglu said the elections would be held under "democratic conditions" and urged the country's political forces to stand "shoulder to shoulder" in a show of unity.

The co-chair of pro-Kurdish Peoples' Democratic Party (HDP), Selahattin Demirtas, called for peace between Turks and Kurds.

"I am calling on all my brothers. No matter what they do... do not harm our brotherhood," Demirtas told reporters.

"Kurds, Turks embrace each other. The best medicine against all the provocations is peace."